P5 Flashcards
What is power transfer in any circuit device related to
power transfer in any circuit device is related to the potential difference across it and the current through it, and to the energy changes over time
What is the equation for power with current and potential difference
Potential difference x current
P = V x I
Equation for power with current and resistance
Current^2 x resistance
P = I^2 x R
What are all electrical appliances designed to do
Transfer energy to components in the circuit when a current flows
What does rhe amount of energy transfer for an appliance depend on
The amount of energy an appliance transfers depends on how long the appliance is switched on for and the power of the appliance
When is work done in a circuit
When current flows
How does a kettle and a fan work
Kettles transfer nergy electrically from the mains ac supply to the thermal energy store of the heating element inside the kettle
Energy is transferred electrically from the battery of a handheld fan to the kinetic energy store of the fans motor
Two equations for energy transferred
energ y trans f erred = power × time
E = P x t
energy transferred = charge flow × potential difference
E = Q x V
What is the power of a circuit device related to
the power of a circuit device is related to:
• the potential difference across it and the current through it
• the energy transferred over a given time
What is the national grid
The National Grid is a system of cables and transformers linking power stations to consumers
How is the national grid used
Electrical power is transferred from power stations to consumers using the National Grid
How are step up and step down transformers used
Step-up transformers are used to increase the potential difference from the power station to the transmission cables then step-down transformers are used to decrease, to a much lower value, the potential difference for domestic use
